People who always need you to be there for them but seem to be conviently preoccupied when you need the same.

Military recruiters

Taxi Drivers

I think what you meant to say is:-

"People who always need you to be there for them but seem to be conviently preoccupied when you need the same, such as, direct supervisors or bosses, sales people, military recruiters and taxi Drivers"

Anyone who walks up to me on the street and offers to sell me a "Brand New Big Screen TV, or VCR, or DVD Player, or XBox360" for $20. And for some reason they always seem way to malnouirshed to be hauiling this stuff around on a ten speed bike at 3 am.

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There are no PERFECT techniques, only perfect execution for the situation at hand.
~Corwin